The present invention relates to magnetic disc storage systems. More specifically, the invention relates to a method and apparatus for determining and adjusting slider fly height in a magnetic disc storage system.
In magnetic storage systems, a magnetic disc rotates at high speed. A read/write transducing head "flies" over the surface of the disc carried on a slider and is used for reading and writing information. The slider has certain hydrodynamic properties which provide lift while the drive rotates. This lift is counteracted by a spring loaded flexure armature which supports the slider. The slider reaches an equilibrium fly height based principally upon the speed of rotation of the disc, the hydrodynamic properties of the slider, and the spring tension of the flexure armature. Typically, fly height can be on the order of tenths of microns or less from the disc surface.
It is known that if the slider and, hence the transducer head, fly closer to the disc surface, improved reading and writing characteristics are achieved. This is primarily due to improved focusing of the magnetic fields exchanged between the head and the disc surface. Typical techniques of reducing fly height have involved controlling the hydrodynamic properties of the slider or the spring tension of the flexure arm during manufacture. As storage density requirements increase, fly height decreases. Fly height becomes even more critical and greater accuracy in controlling fly height is of even greater importance. Adequate clearance must be maintained such that no catastrophic head-disc contact ("crash") occurs during operation when all of the worst case tolerances are statistically added together. Key contributors to these tolerances include run-out in the disc and slider fly height. If these tolerances could be reduced to zero (or, alternatively, were precisely known for each head-disc interface), sliders could confidently fly closer to the disc.